1. Field of the Invention
The present invention is generally related to a coolant management system and, more particularly, to a system and method for cooling the outer surface of an oil sump of an outboard motor by an amount that varies with the operating speed of an internal combustion engine of the outboard motor.
2. Description of the Prior Art
Four cycle engines are provided with an oil reservoir, or sump, which stores liquid lubricant that is used to lubricate moving components of the internal combustion engine and associated parts. It is important that the liquid lubricant is prevented from being overheated by heat generated by the internal combustion engine. It is also important that the temperature of the lubricant in the oil sump be prevented from falling below an appropriate operating range. Various systems and methods are known to those skilled in the art for controlling the operating temperature of a liquid lubricant within an oil sump.
U.S. Pat. No. 6,416,372, which issued to Nozue on Jul. 9, 2002, describes an outboard motor cooling system that includes an improved construction to enhance cooling of the lubricant system. It includes an oil pan of the lubrication system. The oil pan depends from an engine of the outboard motor and into a driveshaft housing. A periphery coolant jacket is provided around the oil pan. A water pool is defined between the oil pan and the driveshaft housing. An exhaust manifold passes through in a hollow of the oil pan and a water curtain is defined between the hollow wall and the exhaust manifold. An upstanding water passage is also disposed through the oil pan. At least one of an upper and lower transverse water jacket extends transversely above or below the oil pan. No drain water from the engine flows through these jackets or passages. The oil pan therefore is sufficiently cooled. In addition, the upper transverse water jacket increases protection of engine components form heat deterioration.
U.S. Pat. No. 6,182,631, which issued to Kitajima et al on Feb. 6, 2001, describes a camshaft for an engine. It also describes a cooling and exhaust system for the engine which are formed with a minimum number of components and sealing joints and which incorporate a non-metallic camshaft for reduced cost and weight without sacrificing durability. The exhaust system includes an elongated expansion chamber formed in the driveshaft housing. In addition, the driveshaft housing has a cylindrical section that is journaled within a swivel bracket for its steering movement. The volume between the external portion of the driveshaft housing and the internal portion of the swivel bracket forms a second expansion chamber that is employed for the low speed above the water exhaust gas discharge. The flow of cooling water to and from the engine is controlled so that the exhaust gas interchange area between the powerhead and the driveshaft housing will be well cooled as will the oil reservoir for the engine and the oil returned to it.
U.S. Pat. No. 6,012,956, which issued to Mishima et al on Jun. 9, 1998, describes a cooling water passage structure of an outboard motor. The outboard motor is equipped with an engine, an engine holder, an oil pan disposed below the engine in a state of the outboard motor being mounted to a hull, a water pump disposed below the oil pan, and a cooling water passage structure. The cooling water passage structure includes a vertical cooling water passage vertically passing through the inside of the oil pan and communicated with the side of the engine, a lateral cooling water passage extending in a lateral direction along a bottom surface of the oil pan, a cooling water supply pipe extending upward from the water pump and connected to a side of the engine, and a water pressure relief valve provided for the lateral cooling water passage for controlling a pressure increase of the cooling water. The lateral cooling waster passage has one end communicated with a lower end of the vertical cooling water passage and has another end to which an upper end of the cooling water supply pipe is connected.
U.S. Pat. No. 5,937,801, which issued to Davis on Aug. 17, 1999, discloses an oil temperature moderator for an internal combustion engine. A cooling system is provided for an outboard motor or other marine propulsion system which causes cooling water to flow in intimate thermal communication with the oil pan of the engine by providing a controlled volume of cooling water at the downstream portion of the water path. As cooling water flows from the outlet of the internal combustion engine, it is caused to pass in thermal communication with the oil pan. Certain embodiments also provide a pressure activated value which restricts the flow from the outlet of the internal combustion engine to the space near the oil pan. One embodiment of the cooling system also provides a dam within the space adjacent to the outer surface of the oil pan to divide that space into first and second portions. The dam further slows the flow of water as it passes in thermal communication with the oil pan.
U.S. Pat. No. 5,934,957, which issued to Sato et al on Aug. 10, 1999, describes an outboard motor having an oil pan positioned on the underside of the engine. It also has an exhaust passage, a water supply passage for cooling water, and a wastewater passage extending down from the engine and passing near the oil pan. The exhaust passage, the water supply passage, and the wastewater passage are molded as a single unit with the oil pan, and provide a simple, lightweight structure that does not result in an increase in the number of parts or assembly man hours necessary for construction. The oil pan is protected from the exhaust heat by the water passages, and a flush port to clean the cooling system is easily accessible.
U.S. Pat. No. 5,876,256, which issued to Takahashi et al on Mar. 2, 1999, describes an engine cooling system. A liquid cooling system for an internal combustion engine of an outboard motor includes a pump for delivering coolant to one or more coolant passages in the engine. At least one thermostat is provided for controlling the flow of coolant through the engine to one or more return lines which extend to a coolant pool extending about a lubricating oil reservoir. A pressure relief valve is provided between the pump and thermostat for relieving coolant from the engine upon excessive coolant pressure. The relief coolant is preferably either delivered to a drain, a second coolant pool extending about a muffler, or the first coolant pool. Preferably, a diverter is provided for controlling the flow of the relieved coolant. When a temperature of the lubricating oil is high, the relief coolant is preferably diverted to the first coolant pool for additional cooling of the oil in the reservoir, and when the temperature of the oil is low, the relieved coolant is preferably either diverted to the second coolant pool or the coolant drain for passage out of the motor.
U.S. Pat. No. 5,704,819, which issued to Isogawa on Jan. 6, 1998, describes an oil pan arrangement for a four cycle outboard motor. The outboard motor has a high performance V-type twin overhead cam four cycle internal combustion engine. The oil reservoir for the engine is disposed in a driveshaft housing below the engine and an oil pump is driven off the lower end of the engine crankshaft for circulating the oil from the oil tank to the engine. The oil supply system for the engine includes a vertically extending main gallery and a drain passage which extends in parallel side-by-side relationship and which are disposed over the oil tank for ease of oil return. The exhaust and cooling system for the engine is configured so as to minimize heat transfer between the exhaust system and the lubricating system and to maintain a compact assembly.
U.S. Pat. No. 5,487,687, which issued to Idzikowski et al on Jan. 30, 1996, discloses a midsection and cowl assembly for an outboard marine drive. The outboard marine drive has a midsection between the upper powerhead and the lower gearcase and has a removable midsection cowl assembly including first and second cowl sections. The midsection housing includes an oil sump in one embodiment and further includes an exhaust passage partially encircled by cooling water and partially encircled by engine oil for muffling engine exhaust noise. The midsection housing also has an oil drum arrangement providing complete and clean oil draining while the outboard drive is mounted on a boat and in the water wherein the operator can change oil without leaving the confines of the boat and entering the water.
U.S. Pat. No. 5,462,464, which issued to Ming on Oct. 31, 1995, describes an outboard motor with an oil sump cooling arrangement. A driveshaft housing includes outer side walls extending in spaced relation to each other, a forwardly located wall extending between the outer side walls, a rearwardly located wall spaced rearwardly from the forwardly located wall and extending between the outer side walls and a bottom wall extending between the outer side walls and between the forwardly and rearwardly located walls. The outer side walls, forwardly and rearwardly located walls, and bottom wall define an oil sump. A cooling passage extends vertically in one of the outer side walls. The forwardly located wall and the rearwardly located wall are adapted adjacent the upper end thereof for connection to a source of coolant. They terminate, at the lower end thereof, in a port located in the bottom wall and a deflector is fixed to the bottom wall and defines, with the bottom wall, a conduit extending along the bottom wall and having one end communicating with the coolant passage and a second end having an elongated discharge area, whereby to provide coolant flow along a substantial portion of the bottom surface of the bottom wall.
U.S. Pat. No. 5,439,404, which issued to Sumigawa on Aug. 8, 1995, describes a cooling system for an outboard motor. The cooling system for an outboard motor and specifically for the lubricating reservoir thereof is described. The lubricating reservoir depends into the driveshaft housing and is surrounded by an open trough-like water manifold to which cooling water is delivered from the engine. This manifold has lower restricted openings that direct the cooling water to the outer peripheral wall of the oil pan of the lubricant reservoir. The water level is maintained by a weir-like structure and the water that overflows the weir is also directed toward the outer surface of the lubricant reservoir.
U.S. Pat. No. 5,232,387, which issued to Sumigawa on Aug. 3, 1993, describes an exhaust device for a four cycle outboard motor. An arrangement is provided for the lubricating, cooling and exhaust systems of a four cycle outboard watercraft motor. Coolant is drawn from the body of water within which the watercraft is operated for circulation through the engine cooling system. Subsequently, the coolant is brought into proximity with an exhaust pipe extending downwardly from the engine within an encasing member. After passing downwardly along the exhaust pipe the coolant is finally directed towards an exhaust gas expansion chamber and a cooling water jacket provided around the expansion chamber. In order to prevent any of the cooling water from splashing back up against an oil reservoir, also located within the casing, a cover is provided across the tops of the expansion chamber and its accompanying cooling water jacket. Cooling water or air may fill the voids separating the various components contained within the encasing. The arrangement is particularly effective in preventing the corrosion of the oil reservoir housing due to back-splashed coolant when the watercraft is operated in saltwater; cooling the components contained within the encasing; and, minimizing heat transfer from higher temperature operating components to lower temperature operating components.
U.S. Pat. No. 5,215,164, which issued to Shibata on Jun. 1, 1993, describes a lubricating device for a four stroke outboard motor. A number of embodiments of outboard motors including dry sump lubricated four cycle internal combustion engines is described. The dry sump lubrication system includes a scavenge pump for drawing lubricant drained from the engine lubricating system through an inlet port and returns it to a dry sump reservoir through an outlet port and a pressure pump that draws lubricant from the dry sump lubricant reservoir through an inlet port and delivers it to the engine lubricating system through an outlet port. At least one of the ports of each of the pumps is positioned above the normal lubricant level in the lubricant reservoir when it is filled with the normal volume of lubricant so as to insure that lubricant will not drain back into the engine when the pump system is not operating. Various arrangements for achieving this result and for cooling the lubricant are described.
U.S. Pat. No. 4,735,590, which issued to Mondek on Apr. 5, 1988, describes a lubrication system for a marine propulsion device. The marine propulsion device comprises a propulsion unit including an internal combustion engine, a pump driven by the engine, a transom bracket for mounting the propulsion unit to the transom of a boat, a fluid reservoir carried by the transom bracket, a fluid cooler is carried by the transom bracket for cooling the fluid contained in the reservoir and a conduit for communicating the cooled oil to the pump is provided.
U.S. Pat. No. 4,498,875, which issued to Watanabe on Feb. 12, 1985, describes an outboard motor. Two embodiments of water cooled, four cycle internal combustion engines used for outboard motors is described. In each embodiment, an arrangement is provided that offers a compact nature and which issued the coolant delivered to the engine for cooling the oil in the oil pan. In addition, an arrangement is provided whereby the exhaust pipe may pass through the oil pan and yet avoid significant heat transfer from the exhaust system to the lubricating system. In each embodiment of the invention, coolant is delivered to this clearance for further cooling the exhaust system. In one embodiment of the invention, an arrangement is provided for limiting the discharge of coolant from the clearance so as to maintain a level of coolant around the exhaust pipe.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
Although it is very important that the oil within an oil reservoir or sump is maintained at a temperature less than an upper limit which can degrade and deteriorate the lubricating characteristics of the oil, it is also very important that the oil in the oil sump or reservoir be maintained at a temperature above a lower limit. In certain situations, the oil in the oil sump can be cooled to an excessive degree, particularly when the internal combustion engine of the marine propulsion device is operating at a low speed. When the internal combustion engine is initially started and while it is operating at relatively low operating speeds, such as idle speed, it is beneficial if the oil in the oil reservoir is allowed to absorb sufficient heat to maintain its temperature within an appropriate temperature range. It would be significantly beneficial if a coolant management system could assist in maintaining the operating temperature of the oil in the oil sump within the desired temperature range while requiring a minimum number of components to accomplish this function.
A coolant management system for a marine propulsion device, made in accordance with a preferred embodiment of the present invention, comprises an internal combustion engine having a coolant passage disposed in thermal communication with at least one heat producing portion of the internal combustion engine, a water pump having an inlet connected in fluid communication with a body of water in which the marine propulsion device is operated and an outlet connected in fluid communication with the coolant passage. It also comprises a cavity formed within the marine propulsion device and an oil reservoir disposed at least partially within the cavity. An inlet passage is connected in fluid communication within the coolant passage and the cavity. A drain passage is connected in fluid communication with the cavity to allow the water to drain from the cavity and return to the body of water in which the marine propulsion device is operated. The drain passage is sized to cause the water within the cavity to rise to a level which is at least partially a function of the operating speed of the internal combustion engine, whereby the magnitude of the surface area of the oil reservoir disposed in thermal communication with the water within the cavity is a function of the operating speed of the internal combustion engine.
In a particularly preferred embodiment of the present invention, the system further comprises a first wall within the cavity which defines a first containment and a second containment. The inlet passage is positioned to conduct water from the coolant passage to the first containment. The drain passage is disposed in the second containment.
In a preferred embodiment of the present invention, the system further comprises a second wall disposed within the second containment to define a first compartment and a second compartment. The drain passage comprises a first opening in the first compartment and a second opening in the second compartment. The first wall has an upper edge that, in one embodiment, is generally straight and, in another embodiment, a portion of the oil reservoir, or sump, is lower than the upper edge of the first wall. The cavity is disposed within a driveshaft housing of the marine propulsion device which, in a preferred embodiment is an outboard motor. The method of the present invention for managing the coolant flow in a marine propulsion device, in a preferred embodiment, comprises the steps of providing a pump for drawing water from a body of water in which the marine propulsion device is operating, directing the water into thermal communication with an internal combustion engine of the marine propulsion device, conducting the water into a cavity formed within the marine propulsion device at a first rate of flow which is a function of the operating speed of the internal combustion engine, wherein the cavity is shaped to contain an oil reservoir of the internal combustion engine, and conducting the water out of the cavity at a second rate of flow, whereby the first and second rates of flow determine the height of a level of water within the cavity as a function of the operating speed of the internal combustion engine.